The majority of present day integrated circuits (ICs) are implemented by using a plurality of interconnected field effect transistors (FETs), also called metal oxide semiconductor field effect transistors (MOSFETs), or simply MOS transistors. An MOS transistor includes a gate electrode as a control electrode and spaced apart source and drain electrodes between which a current can flow. A control voltage applied to the gate electrode controls the flow of current through a channel between the source and drain electrodes. As the complexity of the integrated circuits increases, more and more MOS transistors are needed to implement the integrated circuit function. As more and more transistors are designed into the IC, it becomes important to shrink the size of individual MOS transistors so that the size of the IC remains reasonable and the IC can be reliably manufactured. Shrinking the size of an MOS transistor implies that the minimum feature size, that is, the minimum width of a line or the minimum spacing between lines, is reduced. MOS transistors have now been aggressively reduced to the point at which the gate electrode of the transistor is less than or equal to 20 nanometers (nm) in width. One feature that must be reduced as the transistor size shrinks is the contact opening. A contact opening is the opening through one or more insulating layers that is subsequently filled with a conductive material that forms a contact to a device region and allows interconnections between devices of the IC. The conductive material forming the contact, which often takes the form of a plug, may be tungsten or other metals. A conductive liner is often used to physically isolate the tungsten or other metal from the insulating material surrounding the contact and from the underlying device region. As the size of the contact opening is reduced, the resistance of the contact increases. The increase in resistance can result from an increase in the resistance of the liner material as well as an increase in resistance of the interface between the liner and the plug material. Increases in contact resistance can seriously affect the performance of the IC because any increase in contact resistance increases the resistance-capacitance (RC) time constant of the device.
Accordingly, it is desirable to provide a method of fabricating a semiconductor device that allows small feature size without adversely affecting contact resistance. In addition, it is desirable to provide a method of fabricating a semiconductor device that produces low resistance device contacts. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.